Energy Efficiency in the Refrigeration and Air-Conditioning Sector
← News · 20 May 2026
The return of natural refrigerants
Ammonia, carbon dioxide, propane and isobutane. The fluids refrigeration began with are coming back, this time because of the climate.
Refrigerants have been through several generations. The first industrial systems of the early twentieth century ran on ammonia and carbon dioxide. Then came the freons — CFCs and HCFCs — safe to handle, but in the 1980s they were confirmed to deplete the ozone layer. HFCs were introduced in their place, and only later HFOs. The problem with HFCs is not ozone but climate: some have a global warming potential more than 3,900 times that of carbon dioxide.
Which is why we are returning to where it all started.
Ammonia (R-717)
A natural fluid with zero GWP and zero ODP and excellent thermodynamic properties, reaching temperatures down to −70 °C. It is used mainly in large industrial plants and cold stores, where it delivers high energy efficiency and a fast return on investment. Low cost and availability make it economical, and the system contains no water, which removes the risk of legionella.
Ammonia is classified as B2L — higher toxicity and low flammability. That means a machine room, built-in gas detection and trained personnel. Its distinctive smell helps detect leaks early, but it does not replace detection equipment.
Carbon dioxide (R-744)
With a GWP of 1, CO₂ is the reference point for every other refrigerant. In refrigeration systems it operates transcritically — part of the cycle takes place above the critical point (30.98 °C and 73.8 bar), where the fluid expands like a gas but has the density of a liquid.
Transcritical CO₂ systems have become the standard technology for new supermarkets in Europe. They were first favoured in cold climates, but efficiency improvements have made them viable in warmer southern regions as well.
Propane and isobutane (R-290, R-600a)
Hydrocarbons with a GWP of just 3 and very good efficiency. Class A3 — highly flammable, which limits them to systems with a small charge: domestic refrigerators, display cabinets, small ice machines. Installation must be carried out by a certified technician.
What this means in practice
None of these is a universal solution. The choice depends on equipment type, charge size and site conditions. What they share is that they are not subject to a shrinking quota, which makes them a safer long-term choice than high-GWP HFCs.
Note: market figures on the uptake of transcritical CO₂ systems in Europe have been left out of this text until the source is confirmed.